A number of other experiments were made August 28 and 29, under less favorable conditions.

By securing a white object of considerable size--a horizontally adjusted dinner-plate about 9.5 inches in diameter--to the sounding-line, it was ascertained that (at noon) it was plainly visible at a vertical depth of 33 meters, or 108.27 English feet.

It must be recollected that the light reaching the eye from such submerged objects must have traversed a thickness of water equal to at least twice the measured depth; in the above case, it must have been at least 66 meters, or 216.54 feet.
Furthermore, when it is considered that the amount of light regularly reflected from such a surface as that of a dinner-plate, under large angles of incidence in relation to the surface, is known to be a very small fraction of the incident beam (probably not exceeding three or four per cent.), it is evident that solar light must penetrate to vastly greater depths in these pellucid waters.
Moreover, it is quite certain that if the experiments in relation to the depths corresponding to the limit of visibility of the submerged white disk had been executed in winter instead of summer, much larger numbers would have been obtained.

For it is now well ascertained, by means of the researches of Dr.F.A.Forel of Lausanne, that the waters of Alpine lakes are decidedly more transparent in winter than in summer.

Indeed, it is reasonable that when the affluents of such lakes are locked in the icy fetters of winter, much less suspended matter is carried into them than in summer, when all the sub-glacial streams are in active operation.
Professor Le Conte goes into this subject (as he later does into the subject of the color of Lake Tahoe) somewhat exhaustively in a purely scientific manner and in too great length for the purposes of this chapter, hence the scientific or curious reader is referred to the original articles for further information and discussion.
_Color of the Waters of Lake Tahoe_.